To date Chromium has always supported whatever codecs its bundled copy of libavcodec was compiled with.

Hopefully they do not purposefully constrain the codec support, like Microsoft did. IE9 uses the system's DirectShow plugins, but whitelists the specific codecs because they don't want to dynamically load shitty DivX binaries into the browser and expose them to the DOM. It sucks but it was the right decision considering the circumstances.